Variable compression ratio internal combustion engine



Jan. 24, 1939. K, TsuNEDA 2,145,017

VARIABLE COMPRESSION RATIO INTERNAL COMBUSTION ENGINE Filed Sept. l, 1.936

T0 INLET IAN/F 01.0

55 Md/w' Patented Jan. 24,*.193e

PATENT OFFICE VARIABLE CMPBESSION M UOIIIBUSHON ENGINE Tbuneda, Kyoto, Japan.

anneau semm- 1, me, serai No.

In Japan April 16, 1936 2 Claims.

This invention relates to a variable compression ratio intemal combustion engine having a movable member incorporated in the wall of the combustion engine.

The object of the invention is to provide such a regulating device in which the operation oi the compression ratio regulating mechanism is controlled by an electrical control means responsive to and actuated by variation ot the engine speed and load thereby automatically and quickly regulating the compression ratio and attaining high' thermal eiiiciency of the engine under varying loads.

In internal combustion engines, it is desirable for the purpose of obtaining higher thermal eiiiciency to vary the compression ratio according to the degree of suction which varies according to the load and the engine speed, so that the en gine operates under the maximum compression ratio permissible for each condition, and such variation is especially desirable and advantageous when operating on lighter load.

'Ihis invention is designed to attain such adjustment, and according to this invention the means for varying the compression ratio comprises a movable member or a piston incorporated in the wall of the combustion chamber and means for displacing said movable member or piston, means being provided for electrically controlling the compression ratio varying means.

In the practice of the invention, the compression ratio varying device may be directly controlled electrically, or it may be controlled through the action oi' another source by opening and closing an electric circuit or circuits. The opening and closing o! the controlling electric circuit may be automatically controlled by utilizing the variation of the vacuum in the intake manifold or variation of the explosion gas pressure, which vary according to the engine load. engine speed, etc.

'Ine invention will now be fully described with reference to the accompanying drawing, in whichz- Fig. 1 is a diagrammatic view of an automatic controlling device utilizing the vacuum prevailing in the intake manifold, and

Fig. 2 is a longitudinal section of a mechanism for varying the compression ratio by displacing the position of a movable member forming a portion of the wall of the combustion chamber.

Fig. 3 shows upon a larger scale the arrangement oi' an electric switch used in the invention, and

(cl. 12a-4mn Fig. 4 shows a modified form of the gas servomotor.

In the embodiment shown, the controlling electric circuit is governed by utilizing the variation oi' the vacuum 'in the intake manifold, whereby the inlet or outlet passage of liquid is controlled so that the liquid pressure is varied to eil'ect automatic control of the mechanism for displacing a movable member provided in a portion of the wall of the compression chamben For the sake of convenience, the compression ratio adjusting mechanism will iirst be described.

Referring to the drawing, particularly Fig. 2, forming the upper wall of the combustion chamber I there is a cylinder head 2 which is provided with a cavity 3. Inserted in said cavity 3 there is a piston-like movable member 4 which has a rod 5 extending upwardly. A gear 6 with its bore internally threaded is engaged by said threaded rod I. Engins with said gear 6 is a toothed rack 1. By moving said rack 'I the threaded rod I carrying the movable member 4 is raised or lowered, so that the eiiective volume of the combustion chamber I is varied accordingly. 3 is a working piston; 3 is'an intake valve; IU is a suction pipe or intake manifold; II is a discharge pipe or exhaust manifold; and I2 designates an ignltionplug.

A liquid servo-motor I3 and a gas servo-motor Il are arranged in a tandem relation. The gas servo-motor Il is connected through a pipe i5 to the intake manifold I3, and the piston I 4' is urged by a weak spring It. The liquid servomotor I3 is provided with a servo-motor piston I3 which is urged toward the liquid side by a spring I'I. 'l'o the piston rod I l is connected the above-mentioned toothed rack 'I by vertical arm 1', and thereto is also secured an electric switch I3. This switch comprises two movable contacts 23 and 2l having moving points 2| and 22 respectively and arranged symmetrically with respect to a stop 23. said contacts 23 and 24 being adapted to be-moved into contact with xed contacts 2l and 2C respectively, and slide 2l which is slidable along ably secured to the cylinder head) and is electrically connected with said movable vcontacts 23 and 24, the latter being pulled by springs 29 and 3l. The slide 2l forms an extension of a piston rod 3| of the piston I4 of the aas servo-motor I 4.- A stop 32 is arranged at a predetermined distance from the piston Il'. A rod 33 secured to the switch I3 extends through the stop 32 into the servo-motor cylinder Il, and at its free end it is provided with a head Il. The liquid servo-motor a guide block 21 (which is suit- 4 'unconnectedthmughapipeslmaumhme valve chest 36 which in turn is connected to a liquid reservoir 4l through a discharge pipe 31 at one side and through asupply pipe 3l attbeother. In said supply pipe 331s inserted a liquid supply pump 33. A. discharge valve 4I is normally held in closed position by a spring, and is opened by energization of a solenoid 42. Similarly, a supply valve 43 is normally closed by a spring and is opened by energization of a solenoid 44. 43' is a check valve provided in the delivery of the liquid supply pump 33. 45 is a common conductor. 46'is a source of electric current. 41 is a hand operated switch. 48 and 43' are conductors forming the discharge valve controlling circuit. 4S and 49' are conductors forming'the supply valve controlling circuit. 5l is a cam for operating the liquid supply pump 33. and is iixed on a shaft driven from the crank shaft of the engine. Preferably, the discharge valve 4I is so arranged as to be actuated also by depression of a starter pedal 5I when the invention is applied to motor vehicles.

As the load decreases or the engine speed is raised, the negative pressure or the vacuum in the intake manifold becomes higher, so that the piston I4 of the gas servo-motor I4 is moved towards the right (in Fig. l) against the action of the spring I6, whereby the slide 28 is also moved towards the right (Fig. 1). As a result of rightward movement of the lower point of connection of the springs 29 and 3|, the movable contact 24 comes into contact with the fixed contact 26, thereby closing the circuit comprising the conductors 45, 49, solenoid 44 and the conductor 49'. By energization of the solenoid 44, the supply valve 43 is opened. At this time, the Vdischarge valve 4I is held in closed position by the spring. The liquid in the reservoir 4II is forced into the servo-motor cylinder I3 through the pipes 39 and 35, and acts upon the piston I3', forcing it to the right and consequently the rod I8 and the toothed rack 1. Actuated by said rack 1 through the gear and the threaded rod 5, the piston-like member 4 is lowered, whereby the compression ratio is increased. When the pressure in the gas-servomotor I4 becomes balanced with the vacuum in the intake manifold, the movement of the piston I4' ceases. However, the supply valve circuit remains closed, so that the piston I3 does not stop its movement and the compression ratio changing movement is continued, moving the switch I9 towards the right. When the switch I9 is centralized with respect to the slide 23, the movable contacts 23 and 24 return to the normal open position, opening the supply valve circuit, whereby the supply valve 43 returns to the normal closed position imder the action of the spring. Thus, the supply of liquid is shut oli', and the action of the liquid servo-motor I3 is stopped, thereby maintaining the desired compression ratio.

As the load increases or the engine speed is lowered, the above mentioned parts partake of the reverse movements. Namely, the movable contact 23 comes into contact with the xed contact 25, closing the circuit comprising the conductors 45, 43, solenoid 42 and the conductor 43'. The energized solenoid 42 opens the discharge valve 4I. Whereupon, the piston I3' acted upon by the spring I1 forces the liquid in the servo-motor cylinder I3 back to the reservoir 4l. The toothed rack 1 moves in the reverse direction, and the compression ratio is decreased thereby.

In any event. when increasing or decreasing the compression ratio, the distance of the differential movement of the slide 23 and the electrical switch I3 is limited by the co-operatlon of the stop 32 and the head 34 of the rod 33, so that the movable contacts 23 and 24 are prevented from moving too far preventing correct action of the device or causing breakage of the device.

When it is desired to utilize the exhaust gas pressure in the gas servo-motor I4, the compression spring I6 is provided at the left side of the piston I4' as illustrated in Figure 4. By such modication, the same result may be attained as mentioned above.

In the preferred form of the embodiment of this invention described with reference to the accompanying drawing, it will be understood that the electric power required for the operationof the device is but a small amount of that required for energizing the solenoids for opening the valve which govern the supply and discharge of the liquid, and that the compression ratio varying mechanism is actuated by liquid pressure, and the controlling circuit is opened at suitable times, so that the mechanism is stopped in the position for maintaining the desired compression ratio. By such device, the operation of regulating the compression ratio is automatically and quickly eil'ected with accuracy.

What I claim is:-

l. In a variable compression ratio internal combustion engine, means forming a combustion chamber having a movable wall member, a compressionratio varying mechanism adapted for moving said movable wall member comprising a liquid servo-motor having a servo-motor piston and servo-motor cylinder, said servo-motor cylinder being connected to a source of liquid pressure, a. pipe connecting said liquid servomotor and the liquid source, a controlling valve in said pipe, a gas servo-motor connected to the intake manifold of the engine, a gas servo-motor piston therefor having a piston rod extension, an electric switch, means carried by said piston vrod extension for actuating said switch, a solenoid for actuating said controlling valve, and an electric circuit including said solenoid and said electric switch.

2. In a variable compression ratio internal combustion engine. means forming acombustion chamber having an auxiliary piston member, a compression ratio varying mechanism adapted for moving said auxiliary piston member comprising Ya liquid servo-motor having a servo-motor piston and a servo-motor cylinder, said servo-motor cylinder being connected to a source of liquid pressure, a pipe connecting said liquid servo-motor and the liquid source, a. controlling valve in said pipe, a gas servo-motor connected to the exhaust pipe of the engine, a gas servo-motor piston therefor having a piston rod extension, an electric switch, means carried by said piston rod extension for actuating said switch, a solenoid for actuating said controlling valve, and an electric circuit including said solenoidand said electric switch.

KENJIRO TSUNEDA. 

